// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
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package org.objectweb.asm.tree.analysis;

import java.util.List;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.TryCatchBlockNode;

/**
 * A semantic bytecode interpreter. More precisely, this interpreter only manages the computation of values from other values: it does not manage the transfer of values to or from the stack, and to or from the local variables. This separation allows a generic bytecode {@link Analyzer} to work with various semantic interpreters, without needing to duplicate the code to simulate the transfer of values.
 *
 * @param <V>
 *          type of the Value used for the analysis.
 * @author Eric Bruneton
 */
public abstract class Interpreter<V extends Value> {

	/**
	 * The ASM API version supported by this interpreter. The value of this field must be one of {@link org.objectweb.asm.Opcodes#ASM4}, {@link org.objectweb.asm.Opcodes#ASM5}, {@link org.objectweb.asm.Opcodes#ASM6} or {@link org.objectweb.asm.Opcodes#ASM7}.
	 */
	protected final int api;

	/**
	 * Constructs a new {@link Interpreter}.
	 *
	 * @param api
	 *          the ASM API version supported by this interpreter. Must be one of {@link org.objectweb.asm.Opcodes#ASM4}, {@link org.objectweb.asm.Opcodes#ASM5}, {@link org.objectweb.asm.Opcodes#ASM6} or {@link org.objectweb.asm.Opcodes#ASM7}.
	 */
	protected Interpreter(final int api) {
		this.api = api;
	}

	/**
	 * Creates a new value that represents the given type.
	 *
	 * <p>
	 * Called for method parameters (including <code>this</code>), exception handler variable and with <code>null</code> type for variables reserved by long and double types.
	 *
	 * <p>
	 * An interpreter may choose to implement one or more of {@link Interpreter#newReturnTypeValue(Type)}, {@link Interpreter#newParameterValue(boolean, int, Type)}, {@link Interpreter#newEmptyValue(int)}, {@link Interpreter#newExceptionValue(TryCatchBlockNode, Frame, Type)} to distinguish different types of new value.
	 *
	 * @param type
	 *          a primitive or reference type, or {@literal null} to represent an uninitialized value.
	 * @return a value that represents the given type. The size of the returned value must be equal to the size of the given type.
	 */
	public abstract V newValue(Type type);

	/**
	 * Creates a new value that represents the given parameter type. This method is called to initialize the value of a local corresponding to a method parameter in a frame.
	 *
	 * <p>
	 * By default, calls <code>newValue(type)</code>.
	 *
	 * @param isInstanceMethod
	 *          {@literal true} if the method is non-static.
	 * @param local
	 *          the local variable index.
	 * @param type
	 *          a primitive or reference type.
	 * @return a value that represents the given type. The size of the returned value must be equal to the size of the given type.
	 */
	public V newParameterValue(final boolean isInstanceMethod, final int local, final Type type) {
		return newValue(type);
	}

	/**
	 * Creates a new value that represents the given return type. This method is called to initialize the return type value of a frame.
	 *
	 * <p>
	 * By default, calls <code>newValue(type)</code>.
	 *
	 * @param type
	 *          a primitive or reference type.
	 * @return a value that represents the given type. The size of the returned value must be equal to the size of the given type.
	 */
	public V newReturnTypeValue(final Type type) {
		return newValue(type);
	}

	/**
	 * Creates a new uninitialized value for a local variable. This method is called to initialize the value of a local that does not correspond to a method parameter, and to reset one half of a size-2 value when the other half is assigned a size-1 value.
	 *
	 * <p>
	 * By default, calls <code>newValue(null)</code>.
	 *
	 * @param local
	 *          the local variable index.
	 * @return a value representing an uninitialized value. The size of the returned value must be equal to 1.
	 */
	public V newEmptyValue(final int local) {
		return newValue(null);
	}

	/**
	 * Creates a new value that represents the given exception type. This method is called to initialize the exception value on the call stack at the entry of an exception handler.
	 *
	 * <p>
	 * By default, calls <code>newValue(exceptionType)</code>.
	 *
	 * @param tryCatchBlockNode
	 *          the exception handler.
	 * @param handlerFrame
	 *          the exception handler frame.
	 * @param exceptionType
	 *          the exception type handled by this handler.
	 * @return a value that represents the given {@code exceptionType}. The size of the returned value must be equal to 1.
	 */
	public V newExceptionValue(final TryCatchBlockNode tryCatchBlockNode, final Frame<V> handlerFrame,
			final Type exceptionType) {
		return newValue(exceptionType);
	}

	/**
	 * Interprets a bytecode instruction without arguments. This method is called for the following opcodes:
	 *
	 * <p>
	 * ACONST_NULL, ICONST_M1, ICONST_0, ICONST_1, ICONST_2, ICONST_3, ICONST_4, ICONST_5, LCONST_0, LCONST_1, FCONST_0, FCONST_1, FCONST_2, DCONST_0, DCONST_1, BIPUSH, SIPUSH, LDC, JSR, GETSTATIC, NEW
	 *
	 * @param insn
	 *          the bytecode instruction to be interpreted.
	 * @return the result of the interpretation of the given instruction.
	 * @throws AnalyzerException
	 *           if an error occurred during the interpretation.
	 */
	public abstract V newOperation(AbstractInsnNode insn) throws AnalyzerException;

	/**
	 * Interprets a bytecode instruction that moves a value on the stack or to or from local variables. This method is called for the following opcodes:
	 *
	 * <p>
	 * ILOAD, LLOAD, FLOAD, DLOAD, ALOAD, ISTORE, LSTORE, FSTORE, DSTORE, ASTORE, DUP, DUP_X1, DUP_X2, DUP2, DUP2_X1, DUP2_X2, SWAP
	 *
	 * @param insn
	 *          the bytecode instruction to be interpreted.
	 * @param value
	 *          the value that must be moved by the instruction.
	 * @return the result of the interpretation of the given instruction. The returned value must be {@code equal} to the given value.
	 * @throws AnalyzerException
	 *           if an error occurred during the interpretation.
	 */
	public abstract V copyOperation(AbstractInsnNode insn, V value) throws AnalyzerException;

	/**
	 * Interprets a bytecode instruction with a single argument. This method is called for the following opcodes:
	 *
	 * <p>
	 * INEG, LNEG, FNEG, DNEG, IINC, I2L, I2F, I2D, L2I, L2F, L2D, F2I, F2L, F2D, D2I, D2L, D2F, I2B, I2C, I2S, IFEQ, IFNE, IFLT, IFGE, IFGT, IFLE, TABLESWITCH, LOOKUPSWITCH, IRETURN, LRETURN, FRETURN, DRETURN, ARETURN, PUTSTATIC, GETFIELD, NEWARRAY, ANEWARRAY, ARRAYLENGTH, ATHROW, CHECKCAST, INSTANCEOF, MONITORENTER, MONITOREXIT, IFNULL, IFNONNULL
	 *
	 * @param insn
	 *          the bytecode instruction to be interpreted.
	 * @param value
	 *          the argument of the instruction to be interpreted.
	 * @return the result of the interpretation of the given instruction.
	 * @throws AnalyzerException
	 *           if an error occurred during the interpretation.
	 */
	public abstract V unaryOperation(AbstractInsnNode insn, V value) throws AnalyzerException;

	/**
	 * Interprets a bytecode instruction with two arguments. This method is called for the following opcodes:
	 *
	 * <p>
	 * IALOAD, LALOAD, FALOAD, DALOAD, AALOAD, BALOAD, CALOAD, SALOAD, IADD, LADD, FADD, DADD, ISUB, LSUB, FSUB, DSUB, IMUL, LMUL, FMUL, DMUL, IDIV, LDIV, FDIV, DDIV, IREM, LREM, FREM, DREM, ISHL, LSHL, ISHR, LSHR, IUSHR, LUSHR, IAND, LAND, IOR, LOR, IXOR, LXOR, LCMP, FCMPL, FCMPG, DCMPL, DCMPG, IF_ICMPEQ, IF_ICMPNE, IF_ICMPLT, IF_ICMPGE, IF_ICMPGT, IF_ICMPLE, IF_ACMPEQ, IF_ACMPNE, PUTFIELD
	 *
	 * @param insn
	 *          the bytecode instruction to be interpreted.
	 * @param value1
	 *          the first argument of the instruction to be interpreted.
	 * @param value2
	 *          the second argument of the instruction to be interpreted.
	 * @return the result of the interpretation of the given instruction.
	 * @throws AnalyzerException
	 *           if an error occurred during the interpretation.
	 */
	public abstract V binaryOperation(AbstractInsnNode insn, V value1, V value2) throws AnalyzerException;

	/**
	 * Interprets a bytecode instruction with three arguments. This method is called for the following opcodes:
	 *
	 * <p>
	 * IASTORE, LASTORE, FASTORE, DASTORE, AASTORE, BASTORE, CASTORE, SASTORE
	 *
	 * @param insn
	 *          the bytecode instruction to be interpreted.
	 * @param value1
	 *          the first argument of the instruction to be interpreted.
	 * @param value2
	 *          the second argument of the instruction to be interpreted.
	 * @param value3
	 *          the third argument of the instruction to be interpreted.
	 * @return the result of the interpretation of the given instruction.
	 * @throws AnalyzerException
	 *           if an error occurred during the interpretation.
	 */
	public abstract V ternaryOperation(AbstractInsnNode insn, V value1, V value2, V value3) throws AnalyzerException;

	/**
	 * Interprets a bytecode instruction with a variable number of arguments. This method is called for the following opcodes:
	 *
	 * <p>
	 * INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC, INVOKEINTERFACE, MULTIANEWARRAY and INVOKEDYNAMIC
	 *
	 * @param insn
	 *          the bytecode instruction to be interpreted.
	 * @param values
	 *          the arguments of the instruction to be interpreted.
	 * @return the result of the interpretation of the given instruction.
	 * @throws AnalyzerException
	 *           if an error occurred during the interpretation.
	 */
	public abstract V naryOperation(AbstractInsnNode insn, List<? extends V> values) throws AnalyzerException;

	/**
	 * Interprets a bytecode return instruction. This method is called for the following opcodes:
	 *
	 * <p>
	 * IRETURN, LRETURN, FRETURN, DRETURN, ARETURN
	 *
	 * @param insn
	 *          the bytecode instruction to be interpreted.
	 * @param value
	 *          the argument of the instruction to be interpreted.
	 * @param expected
	 *          the expected return type of the analyzed method.
	 * @throws AnalyzerException
	 *           if an error occurred during the interpretation.
	 */
	public abstract void returnOperation(AbstractInsnNode insn, V value, V expected) throws AnalyzerException;

	/**
	 * Merges two values. The merge operation must return a value that represents both values (for instance, if the two values are two types, the merged value must be a common super type of the two types. If the two values are integer intervals, the merged value must be an interval that contains the previous ones. Likewise for other types of values).
	 *
	 * @param value1
	 *          a value.
	 * @param value2
	 *          another value.
	 * @return the merged value. If the merged value is equal to {@code value1}, this method <i>must</i> return {@code value1}.
	 */
	public abstract V merge(V value1, V value2);
}
